Congenital deafness with a genetic origin affects approximately 1 in 2000 children born every year. Studies of the origins of genetic deafness, and potential treatments, would be greatly facilitated by the development of mouse models of human deafness. Many mouse mutants with auditory impairment already exist, but the majority of the responsible genes are not readily accessible to molecular cloning. To accelerate the understanding of the genetic basis of hearing and deafness, a scheme to simultaneously identify and mutate genes involved in the development of the murine auditory system is proposed here. New lacZ gene trap vectors designed to increase the number of detectable genomic integration sites, and facilitate the identification of beta-galactosidase (beta-gal)- expressing cells will be constructed using molecular cloning techniques. These vectors will be introduced into pluripotent murine embryonic stem (ES) cells, and the resulting cell lines will be screened, both before and after in vitro differentiation,f or beta-gal activity that results from vector integration into an expressed gene. ES cell clones that show a regulated pattern of beta-gal activity in vitro will be used to generate chimeric embryos which will be analyzed for beta-gal activity at various developmental stages. Clones that give rise to beta-gal expression in components of the developing auditory system and/or the surrounding tissues thought to induce the auditory system, will be used to generate mouse strains that carry the gene trap insertions. A genetic analysis will be used to determine whether the disrupted genes give rise to overt mutant phenotypes in the embryonic and/or adult auditory system. Genes important for auditory system development, identified using this approach, can be cloned easily by virtue of their linkage to lacZ sequences, and will subsequently be identified by DNA sequence analysis. The DNA probes that result from this research could potentially be used in future linkage studies to identify genes involved in human disorders.